1. Field of the Invention
The present invention relates to an optical transmission system, monitoring method therefor, an optical communication apparatus, and an optical external conducting apparatus, and relates in particular to an optical transmission system, monitoring method therefor, an optical communication apparatus, and an optical external conducting apparatus, whereby it is possible to perform monitoring of optical signals transmitted and received between the optical communication apparatus and its communicating party.
2. Description of the Related Art
With a multi-access system such as a bus-structure LAN, it is easy to monitor communication data with a monitor via a repeater or the like.
However, with a point-to-point communication method such as ATM (Asynchronous Transfer Mode) communication, for example, it is difficult to use a similar method. Thus, communication data is usually monitored by inserting a monitor that has two sets of transmit/receive ports between the communicating apparatuses.
FIG. 5 is a block diagram of the configuration of a conventional optical transmission system. In FIG. 5, when monitoring of communication data transmitted and received between a communication apparatus 100 and a communication apparatus 200 is performed, a monitor 300 which has a transmit/receive port 400 and a transmit/receive port 500 is inserted between the communication apparatus 100 and the communication apparatus 200.
Then, data transmitted from the communication apparatus 100 is displayed on a display unit 600 and data transmitted from the communication apparatus 200 is displayed on a display unit 700. By this means, it is possible to perform monitoring of communication data transmitted and received between the communication apparatus 100 and the communication apparatus 200.
Also, another conventional technology is the optical transmission system disclosed in Japanese Patent Laid-Open No. 7-38506. The above described publication describes an optical transmission system whereby an optical signal input to the optical fiber amplifier of an optical repeater is branched by an optical coupler, the optical level of this branched optical signal is monitored, and an alarm signal is sent out if the level falls below a predetermined value.
However, in the optical transmission system shown in FIG. 5, the monitor is expensive, and therefore the monitor 300 is normally connected only if a problem occurs in communication between the communication apparatus 100 and the communication apparatus 200. A disadvantage of this is that, in order to connect the monitor 300, it is necessary to connect/disconnect optical fibers during operation and it is unavoidable to interrupt the operation.
Also, in the optical transmission system disclosed in the above described publication, the optical level is monitored, and this system thus has the disadvantage of not being able to handle cases where a fault cannot be judged by the optical level alone, such as when the optical level of the optical signal is normal but there is a problem with the data level.